INFO: rcu_sched self-detected stall on CPU
INFO: rcu_sched detected stalls on CPUs/tasks:
	0-....: (125000 ticks this GP) idle=40a/140000000000001/0 softirq=25106/25106 fqs=31226 
	(detected by 1, t=125002 jiffies, g=14118, c=14117, q=303)
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 7746 Comm: syz-executor4 Not tainted 4.15.0-rc2+ #123
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
RIP: 0010:inb arch/x86/include/asm/io.h:348 [inline]
RIP: 0010:io_serial_in+0x6b/0x90 drivers/tty/serial/8250/8250_port.c:434
RSP: 0018:ffff8801db406ff8 EFLAGS: 00000002
RAX: dffffc0000000000 RBX: 00000000000003fd RCX: 0000000000000000
RDX: 00000000000003fd RSI: 0000000000000005 RDI: ffffffff87cee980
RBP: ffff8801db407008 R08: ffff8801db406b88 R09: ffff8801bd8be040
R10: 000000000000000b R11: ffffed003b680d73 R12: ffffffff87cee940
R13: 0000000000000020 R14: fffffbfff0f9dd6f R15: fffffbfff0f9dd32
FS:  0000000000000000(0000) GS:ffff8801db400000(0063) knlGS:00000000f7717b40
CS:  0010 DS: 002b ES: 002b CR0: 0000000080050033
CR2: 000000009bc28000 CR3: 00000001d8f5a000 CR4: 00000000001406f0
DR0: 0000000020001000 DR1: 0000000020001000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000600
Call Trace:
 <IRQ>
 serial_in drivers/tty/serial/8250/8250.h:111 [inline]
 wait_for_xmitr+0x93/0x1e0 drivers/tty/serial/8250/8250_port.c:2033
 serial8250_console_putchar+0x1f/0x60 drivers/tty/serial/8250/8250_port.c:3170
 uart_console_write+0xac/0xe0 drivers/tty/serial/serial_core.c:1858
 serial8250_console_write+0x647/0xa20 drivers/tty/serial/8250/8250_port.c:3236
 univ8250_console_write+0x5f/0x70 drivers/tty/serial/8250/8250_core.c:590
 call_console_drivers kernel/printk/printk.c:1574 [inline]
 console_unlock+0x788/0xd80 kernel/printk/printk.c:2233
 vprintk_emit+0x4ad/0x590 kernel/printk/printk.c:1757
 vprintk_default+0x28/0x30 kernel/printk/printk.c:1796
 vprintk_func+0x57/0xc0 kernel/printk/printk_safe.c:379
 printk+0xaa/0xca kernel/printk/printk.c:1829
 print_cpu_stall_info_begin kernel/rcu/tree_plugin.h:1657 [inline]
 print_cpu_stall kernel/rcu/tree.c:1594 [inline]
 check_cpu_stall.isra.64+0x845/0x15b0 kernel/rcu/tree.c:1676
 __rcu_pending kernel/rcu/tree.c:3440 [inline]
 rcu_pending kernel/rcu/tree.c:3502 [inline]
 rcu_check_callbacks+0x256/0xd00 kernel/rcu/tree.c:2842
 update_process_times+0x30/0x60 kernel/time/timer.c:1630
 tick_sched_handle+0x85/0x160 kernel/time/tick-sched.c:162
 tick_sched_timer+0x42/0x120 kernel/time/tick-sched.c:1166
 __run_hrtimer kernel/time/hrtimer.c:1211 [inline]
 __hrtimer_run_queues+0x349/0xe10 kernel/time/hrtimer.c:1275
 hrtimer_interrupt+0x1d4/0x5f0 kernel/time/hrtimer.c:1309
 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1025 [inline]
 smp_apic_timer_interrupt+0x14a/0x700 arch/x86/kernel/apic/apic.c:1050
 apic_timer_interrupt+0x9d/0xb0 arch/x86/entry/entry_64.S:795
 </IRQ>
RIP: 0010:inq_canon drivers/tty/n_tty.c:2412 [inline]
RIP: 0010:n_tty_ioctl+0x266/0x2d0 drivers/tty/n_tty.c:2429
RSP: 0018:ffff8801c1a07980 EFLAGS: 00000246 ORIG_RAX: ffffffffffffff11
RAX: 0000000000010000 RBX: ffffc900012ed060 RCX: ffffffff8286b1b6
RDX: 0000000000010000 RSI: ffffc90002a29000 RDI: ffffc900012ee260
RBP: ffff8801c1a079c0 R08: ffff8801c1a073d0 R09: ffff8801bd8be040
R10: 000000000000000b R11: ffffed0038340e7c R12: ffffc900012ec000
R13: 000000048860da1b R14: 000000002058dffc R15: ffff8801c3861778
 tty_ioctl+0x32e/0x15f0 drivers/tty/tty_io.c:2638
 vfs_ioctl fs/ioctl.c:46 [inline]
 do_vfs_ioctl+0x1b1/0x1530 fs/ioctl.c:686
 C_SYSC_ioctl fs/compat_ioctl.c:1495 [inline]
 compat_SyS_ioctl+0x4ef/0x2a30 fs/compat_ioctl.c:1419
 do_syscall_32_irqs_on arch/x86/entry/common.c:327 [inline]
 do_fast_syscall_32+0x3ee/0xf9d arch/x86/entry/common.c:389
 entry_SYSENTER_compat+0x51/0x60 arch/x86/entry/entry_64_compat.S:125
RIP: 0023:0xf7f1bc79
RSP: 002b:00000000f771708c EFLAGS: 00000296 ORIG_RAX: 0000000000000036
RAX: ffffffffffffffda RBX: 0000000000000014 RCX: 000000000000541b
RDX: 000000002058dffc RSI: 0000000000000000 RDI: 0000000000000000
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
Code: 24 d9 00 00 00 49 8d 7c 24 40 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 d3 e3 80 3c 02 00 75 17 41 03 5c 24 40 89 da ec <5b> 0f b6 c0 41 5c 5d c3 e8 68 cd 18 ff eb c2 e8 c1 cd 18 ff eb 
INFO: rcu_sched detected expedited stalls on CPUs/tasks: { 0-... } 125570 jiffies s: 1337 root: 0x1/.
blocking rcu_node structures:
Task dump for CPU 0:
syz-executor4   R  running task    22944  7746   3387 0xa002000c
Call Trace:
	0-....: (125000 ticks this GP) idle=40a/140000000000001/0 softirq=25106/25106 fqs=31481 
	 (t=126032 jiffies g=14118 c=14117 q=303)
NMI backtrace for cpu 0
CPU: 0 PID: 7746 Comm: syz-executor4 Not tainted 4.15.0-rc2+ #123
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 <IRQ>
 __dump_stack lib/dump_stack.c:17 [inline]
 dump_stack+0x194/0x257 lib/dump_stack.c:53
 nmi_cpu_backtrace+0x1d2/0x210 lib/nmi_backtrace.c:103
 nmi_trigger_cpumask_backtrace+0x122/0x180 lib/nmi_backtrace.c:62
 arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:38
 trigger_single_cpu_backtrace include/linux/nmi.h:156 [inline]
 rcu_dump_cpu_stacks+0x186/0x1d5 kernel/rcu/tree.c:1459
 print_cpu_stall kernel/rcu/tree.c:1608 [inline]
 check_cpu_stall.isra.64+0xbb8/0x15b0 kernel/rcu/tree.c:1676
 __rcu_pending kernel/rcu/tree.c:3440 [inline]
 rcu_pending kernel/rcu/tree.c:3502 [inline]
 rcu_check_callbacks+0x256/0xd00 kernel/rcu/tree.c:2842
 update_process_times+0x30/0x60 kernel/time/timer.c:1630
 tick_sched_handle+0x85/0x160 kernel/time/tick-sched.c:162
 tick_sched_timer+0x42/0x120 kernel/time/tick-sched.c:1166
 __run_hrtimer kernel/time/hrtimer.c:1211 [inline]
 __hrtimer_run_queues+0x349/0xe10 kernel/time/hrtimer.c:1275
 hrtimer_interrupt+0x1d4/0x5f0 kernel/time/hrtimer.c:1309
 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1025 [inline]
 smp_apic_timer_interrupt+0x14a/0x700 arch/x86/kernel/apic/apic.c:1050
 apic_timer_interrupt+0x9d/0xb0 arch/x86/entry/entry_64.S:795
 </IRQ>
RIP: 0010:inq_canon drivers/tty/n_tty.c:2412 [inline]
RIP: 0010:n_tty_ioctl+0x266/0x2d0 drivers/tty/n_tty.c:2429
RSP: 0018:ffff8801c1a07980 EFLAGS: 00000246 ORIG_RAX: ffffffffffffff11
RAX: 0000000000010000 RBX: ffffc900012ed060 RCX: ffffffff8286b1b6
RDX: 0000000000010000 RSI: ffffc90002a29000 RDI: ffffc900012ee260
RBP: ffff8801c1a079c0 R08: ffff8801c1a073d0 R09: ffff8801bd8be040
R10: 000000000000000b R11: ffffed0038340e7c R12: ffffc900012ec000
R13: 000000048860da1b R14: 000000002058dffc R15: ffff8801c3861778
 tty_ioctl+0x32e/0x15f0 drivers/tty/tty_io.c:2638
 vfs_ioctl fs/ioctl.c:46 [inline]
 do_vfs_ioctl+0x1b1/0x1530 fs/ioctl.c:686
 C_SYSC_ioctl fs/compat_ioctl.c:1495 [inline]
 compat_SyS_ioctl+0x4ef/0x2a30 fs/compat_ioctl.c:1419
 do_syscall_32_irqs_on arch/x86/entry/common.c:327 [inline]
 do_fast_syscall_32+0x3ee/0xf9d arch/x86/entry/common.c:389
 entry_SYSENTER_compat+0x51/0x60 arch/x86/entry/entry_64_compat.S:125
RIP: 0023:0xf7f1bc79
RSP: 002b:00000000f771708c EFLAGS: 00000296 ORIG_RAX: 0000000000000036
RAX: ffffffffffffffda RBX: 0000000000000014 RCX: 000000000000541b
RDX: 000000002058dffc RSI: 0000000000000000 RDI: 0000000000000000
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000